Three dimensional behaviour of bituminous mixtures in the linear viscoelastic and viscoplastic domains: The DBN model

Behaviour of bituminous mixtures is very complex. Their rheological properties depend on strain amplitude level and temperature. We can observe linear viscoelasticity properties for very small strain amplitudes and non-linearities for larger strain levels. Fatigue and rutting (permanent deformation) can appear for a great number of cycles. Moreover brittle or ductile failure can occur. All of these properties strongly temperature and time dependant. The DBN (Di Benedetto-Neifar) model developed at LGCB laboratory (University of Lyon/ENTPE "Ecole Nationale des TPE") aims at describing the complex behaviour of bituminous mixtures with an unified formalism. The model is also versatile and may be adapted to take into account some specific properties of bituminous materials. First, equations describing the whole three-dimensional DBN model in the linear domain are proposed. Then the visco-plastic formalism is introduced in the Elastic-Perfectly Plastic (EPP) case which is a simplified version of the model proposed for numerical finite element calculations. Calibration of the model in the viscoelastic and viscoplastic domains as well as simulation are proposed based on experiments made at LGCB laboratory for different loading paths in the small and large strain domains.